Forged flanges are pipe connection components manufactured through forging processes (hot or cold forging), where metal billets such as carbon steel, stainless steel, or alloy steel are plastically deformed under high pressure. They are used for sealing and supporting in piping systems.
Forged flanges offer superior mechanical properties and reliability compared to cast alternatives, featuring a dense, uniform grain structure that provides 30% higher tensile strength and excellent fatigue resistance. The forging process eliminates internal defects like porosity, ensuring exceptional performance in high-pressure (up to Class 2500) and extreme temperature applications (-196°C to +538°C).
As a specialized forged flange manufacturing enterprise, SSM possesses extensive experience in flange processing and in-depth knowledge of forged flange production workflows. Below, we will share the detailed manufacturing process of forged flanges, which we hope will be valuable to you.
Step 01 Raw Material Selection
To produce superior forged flanges, the first and most critical step is raw material selection. Only by using qualified materials can the performance of the final product be guaranteed.
For efficiency and reliability, it is often best to source materials from reputable suppliers—while their prices may not be the most competitive, their materials strictly comply with international standards, and their brand reputation serves as a quality endorsement for high-performance forged flanges.
Common Material Standards for Forged Flanges
| Material Category | International Standards | Common Grades | Key Applications |
| Carbon Steel | ASTM A105, EN 10222-2 P355NH, JIS G3201 SS400 | C22.8, C21, RSt37.2, S235JRG2, A516 Gr.70 | General piping, low-pressure systems |
| Low-Temp Carbon Steel | ASTM A350 LF2, EN 10222-2 P265GH | L290, L360, L415 | Cryogenic storage, LNG terminals |
| Stainless Steel | ASTM A182 F304/F316, EN 1.4301/1.4401 | F304L, F316L, F316Ti, F321 (1.4541), 1.4571 | Chemical processing, food/pharma |
| Duplex Steel | ASTM A182 F51/F53, EN 1.4462/1.4410 | UNS S31803 (2205), UNS S32750 (2507) | Offshore platforms, seawater systems |
| High-Alloy Steel | ASTM A182 F11/F12, ASTM A694 F60/F70 | 1.0565, A182 F11 (Cr-Mo), F52/F65 (High-yield) | Power plants, high-temperature service |
Step 02 Material Inspection
After the raw materials are received and stored, they must undergo inspection before starting the production of new forged flanges.
This ensures that materials are not mixed up and provides an additional quality check through a standardized process.
At this stage, the chemical composition and mechanical properties of the raw materials are typically tested.
Step 03 Cutting
According to the order requirements, the type and quantity of raw materials are calculated, followed by cutting.
Accurate calculation helps avoid material waste and prevents errors that could lead to repeated processes and delays in delivery.
Step 04 Heating
Before forging, the cut materials must be heated to increase the metal’s plasticity and reduce deformation resistance, making it easier for the raw material to be shaped during the forging process while minimizing the risk of cracking or damage.
It is important to note that different materials require different heating temperatures.
| Material Type | Heating Temperature Range (°C) | Notes |
| Carbon Steel (e.g., A105) | 1150°C – 1250°C | Commonly used for general forging |
| Stainless Steel (304/316) | 1100°C – 1200°C | Uniform heating required to avoid oxidation |
| Alloy Steel (e.g., 42CrMo) | 1100°C – 1180°C | Cooling must be controlled to avoid cracking |
| Duplex Stainless Steel (2205) | 1100°C – 1250°C | Requires strict control of time and temperature |
| Nickel Alloys (e.g., Inconel) | 1000°C – 1150°C | Excessive heat can cause grain growth |
Step 05 Forging
Depending on the specific product requirements, we adopt various forging methods including ring rolling, drop forging, open die forging, and closed die forging to ensure optimal performance and precision.
| Forging Type | Description | Applications | Advantages |
| 1. Ring Rolling | Heating the metal and using rollers to expand the inner diameter and reduce wall thickness. | Suitable for ring-shaped workpieces (e.g., flanges, bearing rings) | Dense structure, high dimensional accuracy. |
| 2. Drop Forging | Metal is rapidly shaped by a hammer and die. | Suitable for medium and small batch parts | High precision, but mold cost is higher. |
| 3. Open Die Forging | Repeated hammering between an upper and lower die to shape the metal. | Suitable for large or irregularly shaped workpieces | Low cost, high machinability. |
| 4. Closed Die Forging | Metal is shaped in precise molds. | Suitable for complex shapes and large-scale production | High dimensional accuracy, smooth surface. |
Step 06 Heat Treatment
Heat treatment (Annealing, Normalizing, Solution Treatment) is a process that changes the internal structure and properties of metals by controlling the heating, holding, and cooling processes.
These heat treatment processes can be selected according to different material requirements to ensure that the metal materials achieve optimal performance during production and meet the demands of the final application.
Step 07 Machining
Forged flange machining refers to the precise machining of a flange after it has been forged, in order to achieve the required dimensions, shape, and surface finish.
After the forging process, the flange’s surface may be uneven or have dimensional deviations, and machining can further optimize these issues, ensuring that the flange meets strict technical requirements.
It can be ultimately machined to shape according to specifications and customer customization needs.
Step 08 Checking
UT (Ultrasonic Testing) and PMI (Positive Material Identification) are two different testing methods used for quality control of rough-processed products, particularly in metals and alloys.
UT is used to detect internal defects or issues within the material.
PMI is used to ensure the correct chemical composition of the material by analyzing the elements within it.
These tests are essential for ensuring the integrity and quality of rough-processed products before further processing or use in critical applications.
Step 09 Drilling
The product is drilled with a CNC drilling machine.
In this step, various holes in the flange are processed, and it is crucial to follow the dimensions precisely.
Any deviation from the required measurements can result in wasted effort, additional costs, and delays in the production schedule.
Step 10 Inspection
According to customer requirements, quality inspection personnel carry out various inspections on the product, including Dimension Inspection, Bevel Angle Inspection, Roughness Inspection, Surface Hardness Test, UT (Ultrasonic Testing), MT (Magnetic Particle Testing), PT (Penetrant Testing), and PMI (Positive Material Identification).
These tests ensure that the product meets all specified standards and customer expectations, and help to verify the material properties, surface quality, and structural integrity of the product.
Step 11 Marking
Type on products according to different specifications and customer requirements. This helps customers cross-check the items upon receipt and prevents confusion when using the products later.
An example of labeling for ASME B16.5 flanges: ASME B16.5 150# 6″ Weld Neck Flange 304 Stainless Steel
- Explanation:
- ASME B16.5: The flange standard (ASME B16.5).
- 150#: The pressure rating (150 pounds).
- 6″: The size or nominal diameter of the flange (6 inches).
- Weld Neck: The flange type (Weld Neck Flange).
- 304 Stainless Steel: The material of the flange (304 Stainless Steel).
Step 12 Surface Treatment
According to different standards or customer requirements, the following surface treatments can be used:
- Anti-rust oil: A protective oil used to prevent rust.
- Yellow, black, blue, green, or red paint: Different colors of paint applied for marking or protection.
- Hot dipping galvanize: Immersing the product in molten zinc to form a zinc coating that prevents corrosion.
- Shot blasting treatment: A process where abrasive materials are shot at the surface to remove impurities and improve surface quality.
- Coating with nylon or Fusion Bonded Epoxy: Applying a nylon or epoxy coating to enhance the product’s durability and corrosion resistance.
These treatments can be applied based on specific requirements for protection, appearance, or performance.
Step 13 Packing
Packaging is the final step and a very important process.
First, the finished products should be properly protected during packaging.
They should be arranged reasonably in plywood boxes and pallets, with a packing list prepared and attached to the correct boxes and pallets. Good, qualified packaging often gives customers a positive impression and is an essential part of quality management.
Now, all that’s left is to wait for shipment.
Step 14 Shipment
Currently, we use four main shipping methods: express delivery, air freight, rail transport, and sea freight.
Small samples of forged flanges can be shipped via express delivery, while more urgent orders or those weighing between 100kg and 300kg can be sent via air freight.
For shipments over 500kg, rail transport is also a good option due to its timeliness and cost-effectiveness, usually at one-fifth the price of air freight. Of course, sea freight is the most cost-effective option, but the delivery time typically exceeds 30 days.
Depending on your specific needs, we can choose the most suitable shipping method. We offer FOB, CIF, and DDP shipping terms. If you’re looking for forged flanges, feel free to contact us.
Summary of Flange Forging
The forging of flanges is a comprehensive process that involves the selection and inspection of raw materials, precise cutting, controlled heating to improve metal plasticity, and forging through various methods such as ring rolling, drop forging, open die forging, or closed die forging. This is followed by heat treatment to enhance mechanical properties, and precision machining to ensure accurate dimensions and surface finish.
For quality control, thorough inspections are carried out using methods such as Ultrasonic Testing (UT), Magnetic Particle Testing (MT), and Positive Material Identification (PMI).
Based on customer requirements, surface treatments such as anti-rust oil application or hot-dip galvanizing can be performed.
Finally, the products are carefully packaged and shipped by express, air, rail, or sea. This entire process ensures the high quality and reliability of forged flanges, meeting the demands of various industrial applications.
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